Outside Air Shut-Off Container and Pressure-Reducible Processing Apparatus

ABSTRACT

Because an O-ring of synthetic resin is pyrolyzed in the atmosphere at a high temperature of 150° C. or more, the airtightness cannot be maintained. In an outside air shut-off container according to the present invention, an inert gas is supplied between an O-ring, which hermetically seals a process chamber and a cover member, and the outside air while a gas passage formed between the O-ring and the outside air is covered with a sealing cover. Additionally, an aluminum oxide layer is formed on a contact surface of the O-ring to increase the pyrolysis temperature of the O-ring.

This application is based upon and claims the benefit of priority from Japanese patent application No. 2010-132329, filed on Jun. 9, 2010, the disclosure of which is incorporated herein in its entirety by reference.

BACKGROUND

1. Field of the Invention

The present invention relates to an outside air shut-off container and a pressure-reducible processing apparatus having a hermetically sealing mechanism.

2. Description of the Related Art

Generally, a pressure-reducible processing apparatus such as a plasma processing apparatus has an outside air shut-off container including a process chamber that houses a substrate to be processed or the like and a cover member mounted on the process chamber. The pressure-reducible processing apparatus conducts plasma processing or the like in a state in which the outside air shut-off container has been decompressed.

Some pressure-reducible processing apparatuses have a hermetically sealing mechanism provided between a process chamber and a cover member in order to hermetically seal the process chamber and the cover member. In a case where such a hermetically sealing mechanism includes an O-ring made of synthetic resin, the synthetic resin has permeability to water or impurity gas (particularly oxygen gas) at a high temperature of 120° C. or more. Therefore, the airtightness of the apparatus cannot be maintained at high temperatures.

Patent Document 1 (WO2009/060756A1) discloses a pressure-reducible processing apparatus capable of maintaining the airtightness even if a process chamber is heated to a high temperature. In a plasma processing apparatus disclosed in Patent Document 1, annular O-rings are doubly provided on a contact surface between a process chamber and a cover member. An inert gas such as an argon gas or a nitrogen gas is supplied to a gap between the two O-rings. The O-rings of Patent Document 1 are made of synthetic resin such as fluororubber.

Thus, O-rings made of synthetic resin are doubly provided in an annular form, and an inert gas is supplied to a gap between the inner O-ring and the outer O-ring so as to form an annular inert gas layer between the inside and outside of the process chamber. Therefore, a gas is prevented from flowing out of the process chamber and flowing into the process chamber.

Furthermore, an O-ring made of synthetic resin exhibits a property in which water, impurity gas, or the like is permitted to pass through the O-ring if the temperature reaches 150° C. With the double annular O-rings as described above, however, the inert gas layer formed in the gap between the O-rings serves as a sealing member even if the O-rings have such permeability. Therefore, the airtightness of the process chamber can be maintained.

Patent Document 1 also discloses an example in which a plurality of gas inlets are formed outside of a single O-ring so that an inert gas flows from those gas inlets to the outside of a process chamber. Thus, an annular inert gas layer is formed between the inside and outside of the process chamber. Therefore, a gas is prevented from flowing into the process chamber and flowing out of the process chamber.

SUMMARY

It is an object of the present invention to provide an outside air shut-off container and a pressure-reducible processing apparatus capable of maintaining sufficient airtightness at high temperatures ranging from 150° C. to 180° C. without an increased number of O-rings.

Furthermore, the present invention intends to solve problems caused when an inert gas is supplied to an outside of a single O-ring.

The present invention is based upon the inventors' findings that the temperature at which pyrolysis of synthetic resin for an O-ring takes place is lowered in the atmosphere and that synthetic resin for an O-ring is likely to be pyrolyzed in a high-temperature state by a catalytic action depending upon a material with which the O-ring is brought into contact.

According to the present invention, a pressure-reducible processing apparatus capable of preventing degradation of an O-ring due to pyrolysis can be provided by improving a contact surface with which the O-ring is brought into contact and/or by avoiding exposing the O-ring to the atmosphere at high-temperatures.

Specifically, the temperature at which pyrolysis takes place is decreased in the atmosphere, and pyrolysis takes place early in a process chamber used at a high temperature. In consideration of those facts, according to an aspect of the present invention, there is provided a pressure-reducible processing apparatus in which an inert gas is supplied to the outside of an O-ring (between the O-ring and the outside air) so as to prevent the O-ring from being brought into contact with the atmosphere. In this case, a replaceable sealing cover is provided on a flange disposed outside of a single O-ring without use of double O-rings. An inert gas is supplied to between the O-ring and the sealing cover. With this configuration, the amount of inert gas flowing outside of the O-ring can be reduced.

Furthermore, when a resin is brought into contact with a contact surface in a high-temperature state, it is likely to be pyrolyzed by a catalytic action with the contact surface. In consideration of this fact, according another aspect of the present invention, there is provided a pressure-reducible processing apparatus in which an aluminum oxide layer is formed at least on a wall surface of an outside air shut-off container with which an O-ring is brought into contact so as to suppress the catalytic action. This aluminum oxide layer is formed by selective formation of a protective film of aluminum oxide through oxidation of anodizing a surface of a chamber that is made of aluminum alloy with a nonaqueous solvent or through thermal oxidation of a surface of stainless steel that contains aluminum.

Furthermore, according to another aspect of the present invention, there is provided an outside air shut-off container in which an inert gas is supplied outside of a single O-ring (between a single O-ring and the outside air) while a replaceable sealing cover is provided on a flange disposed outside of the O-ring.

According to the present invention, there are provided an outside air shut-off container and a pressure-reducible processing apparatus capable of preventing degradation of the airtightness due to pyrolysis of an O-ring made of synthetic resin that is used at a high temperature of 150° C. to 180° C. and capable of reducing the amount of inert gas flowing between the O-ring and the outside air.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view schematically showing a pressure-reducible processing apparatus according to a first embodiment of the present invention.

FIG. 2 is a plan view showing a state in which a cover member has been removed from the pressure-reducible processing apparatus shown in FIG. 1.

FIG. 3 is an enlarged partial view showing a pressure-reducible processing apparatus according to a second embodiment of the present invention.

FIG. 4A is a diagram explanatory of the compressibility of an O-ring.

FIG. 4B is a diagram explanatory of the compressibility of an O-ring.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, a pressure-reducible processing apparatus according to a first embodiment of the present invention is formed by, for example, a plasma processing apparatus having an outside air shut-off container 10 as illustrated. The illustrated outside air shut-off container 10 has a process chamber 12 that defines a processing space therein, a cover member 14 mounted on the process chamber 12, and a hermetically sealing mechanism portion 16 for hermetically sealing the process chamber 12 and the cover member 14. The illustrated process chamber 12 has a cylindrical shape. The process chamber 12 and the cover member 14 are made of aluminum or stainless steel.

The process chamber 12 has an upper end extending outward along its circumference so as to form a chamber protrusion, or a flange portion 12 a. The cover member 14 has a lower end extending outward from its sidewall so as to form a cover member protrusion 14 a.

A gas inlet is formed in the flange portion 12 a of the illustrated process chamber 12 to supply an inert gas such as argon or nitrogen. A gas outlet is formed in the flange portion 12 a to discharge the inert gas. Furthermore, a gas supply pipe 18 and a gas discharge pipe 19 are attached to the gas inlet and the gas outlet, respectively. The gas supply pipe 18 is connected to an inert gas source 20.

A single O-ring 22 is disposed on an inner side of the gas inlet in the flange portion 12 a of the process chamber 12 along an inner edge of the flange portion 12 a. The O-ring 22 is made of synthetic resin such as perfluoroelastomer. The O-ring 22 serves to hermetically seal the process chamber 12 and the cover member 14. Accordingly, the flange portion 12 a and the cover member protrusion 14 a are hermetically sealed by the O-ring 22 when the cover member 14 is mounted on the upper end of the process chamber 12.

Thus, the O-ring 22 constitutes part of the hermetically sealing mechanism portion 16 for hermetically sealing the process chamber 12 and the cover member 14. The illustrated hermetically sealing mechanism portion 16 further includes a sealing cover 25 attached along an outer circumference of the flange portion 12 a of the process chamber 12 and an outer circumference of the cover member protrusion 14 a. The sealing cover 25 may be in the form of a tape.

A gas passage is defined between the O-ring 22 and the sealing cover 25 when the sealing cover 25 is attached to the outer circumference of the flange portion 12 a and the outer circumference of the cover member protrusion 14 a so as to hermetically seal the process chamber 12 and the cover member 14. The illustrated gas passage is formed in a space surrounded by the flange portion 12 a of the process chamber 12, the cover member protrusion 14 a of the cover member 14, the O-ring 22, and the sealing cover 25. The illustrated hermetically sealing mechanism portion 16 is constituted by the flange portion 12 a, the cover member protrusion 14 a, the O-ring 22, and the sealing cover 25, which define the gas passage.

As is apparent from the plan view shown in FIG. 2, the flange portion 12 a of the process chamber 12 is provided so as to surround an inner processing space S. The O-ring 22 is provided on the flange portion 12 a near the inner processing space S. Furthermore, the sealing cover 25 is attached to the outer circumference of the flange portion 12 a. An inert gas such as argon or nitrogen is supplied into a space between the O-ring 22 and the sealing cover 25 from the gas inlet attached to the gas supply pipe 18 and is discharged from the gas discharge pipe 19 connected to the gas outlet.

With this structure, an inert gas is provided between the O-ring 22 and the outside air. Therefore, the O-ring 22 is not exposed to the atmosphere even if the inner processing space S of the outside air shut-off container 10 is heated to 150° C. to 180° C. Accordingly, degradation of the characteristics of the O-ring 22 can be prevented.

A plurality of gas inlets and gas outlets may be provided.

Meanwhile, according to the inventors' study, it has been found that, when the O-ring 22 is made of synthetic resin such as perfluoroelastomer and exposed to the atmosphere, the pyrolysis characteristics of the O-ring 22 vary depending upon the material of a contact surface with which the O-ring 22 is brought into contact. For example, as disclosed in Patent Document 1, it is assumed that the process chamber 12 and the cover member 14 are made of aluminum and that the O-ring 22 is made of synthetic resin and brought into contact with aluminum. The pyrolysis of the O-ring 22 takes place at about 130° C. even if the aluminum used is A5052, which have excellent corrosion resistance. Therefore, if the temperature of the outside air shut-off container 10 becomes 150° C. or more, the characteristics of the O-ring 22 are degraded.

Furthermore, it has been found that the pyrolysis temperature of the O-ring 22 is lowered in the atmosphere when the process chamber 12 and the cover member 14 are made of stainless steel such as SUS316L.

An outside air shut-off container according to a second embodiment of the present invention will be described below with reference to FIG. 3, which shows part of FIG. 1 in an enlarged manner. In FIG. 3, the flange portion 12 a of the process chamber 12 and the cover member protrusion 14 a of the cover member 14 are formed of high-purity aluminum (S2M). Aluminum oxide layers 121 and 141 are provided at least in surface areas of the flange portion 12 a and the cover member protrusion 14 a of the cover member 14 with which the O-ring 22 is brought into contact.

Thus, with the aluminum oxide layers provided on the flange portion 12 a and the cover member protrusion 14 a, which are made of aluminum, the temperature at which pyrolysis takes place in the atmosphere (1% H₂O/20% O₂/Ar) can be increased to 150° C. or more. Therefore, degradation of the O-ring 22 due to pyrolysis can be prevented even though the O-ring 22 is heated to a high temperature.

An anodizing process using a nonaqueous solvent can be used to form the aluminum oxide layers 121 and 141 on the surfaces of the flange portion 12 a and the cover member protrusion 14 a, which are made of aluminum. A method disclosed in JP-A 2008-179884 may be used for an anodizing process using a nonaqueous solvent. An aluminum alloy in which Ce has been added at 1% may be used to form the flange portion 12 a and the cover member protrusion 14 a, and aluminum oxide layers 121 and 141 may be formed by anodizing a surface of the aluminum alloy. The aluminum oxide layers thus produced bring the same advantages as described above. Specifically, the pyrolysis temperature of the O-ring 22 can be increased to 150° C. or more by forming the aluminum oxide layers 121 and 141 on the surfaces of aluminum or aluminum alloy and bringing the O-ring 22 into contact with the aluminum oxide layers 121 and 141.

Furthermore, it has also been found that the pyrolysis temperature of the O-ring 22 made of synthetic resin is 130° C. or less in the atmosphere when the O-ring 22 is brought into contact with the process chamber 12 and the cover member 14 made of stainless steel (SUS). In this case, the pyrolysis temperature of the O-ring 22 can be increased to 150° C. or more by forming aluminum oxide layers 121 and 141 at least on portions of the process chamber 12 and the cover member 14 with which the O-ring 22 is brought into contact.

In order to form an aluminum oxide layer on a surface of stainless steel, a protective film of aluminum oxide may be formed by thermal oxidation of the surface of stainless steel containing aluminum. For example, a method disclosed in JP-A 2004-262133 may be used for the thermal oxidation of stainless steel containing aluminum to form an aluminum oxide layer. Specifically, stainless steel containing iron, chromium, and nickel in addition to aluminum may be oxidized in such an oxidizing atmosphere that only aluminum is oxidized to thereby form a passivation layer of aluminum oxide. The oxidizing atmosphere in which only aluminum is oxidized is preferably an atmosphere having an oxygen concentration of 500 ppb to 100 ppm and a water concentration of 200 ppb to 50 ppm. It is preferable to use an oxidizing mixture gas that includes hydrogen in an oxidizing gas. In this case, oxidation is performed at a temperature ranging from 700° C. to 1,200° C. for 30 minutes to 3 hours to form aluminum oxide layers 121 and 141.

According to the inventors' study, it has been found that the pyrolysis temperature of the O-ring 22 is lowered as the O-ring 22 has a higher compressibility (%).

Now a method of calculating the compressibility (%) will be described below with reference to FIGS. 4A and 4B. When an O-ring 22 having a diameter D as shown in FIG. 4A is compressed and squashed as shown in FIG. 4B, the compressibility (%) is calculated by

compressibility (%)=(PID)×100

where P is the amount of squash.

If the compressibility (%) thus measured exceeds 30%, the O-ring 22 made of synthetic resin tends to be pyrolyzed at a temperature lower than 150° C. Therefore, it is preferable to use the O-ring 22 with a compressibility of about 10% to about 30%. 

1. An outside air shut-off container comprising: a chamber; a cover member mounted on the chamber; and a hermetically sealing mechanism portion for hermetically sealing the chamber and the cover member, the hermetically sealing mechanism portion having: a gas passage defined between the chamber and the cover member, and a sealing portion for sealing the gas passage, the sealing portion including an O-ring and a sealing cover provided between the O-ring and outside air.
 2. The outside air shut-off container as recited in claim 1, wherein the O-ring is made of resin.
 3. The outside air shut-off container as recited in claim 2, further comprising: at least one inlet for supplying an inert gas to the gas passage between the O-ring and the sealing cover; and at least one outlet for discharging the inert gas from the gas passage between the O-ring and the sealing cover.
 4. The outside air shut-off container as recited in claim 2, further comprising: a plurality of inlets for supplying an inert gas to the gas passage between the O-ring and the sealing cover; and a plurality of outlets for discharging the inert gas from the gas passage between the O-ring and the sealing cover.
 5. The outside air shut-off container as recited in claim 1, wherein the O-ring is compressed at a compressibility of 10% to 30%.
 6. A pressure-reducible processing apparatus comprising: a process chamber having a processing space defined therein; a cover member mounted on the process chamber; and a hermetically sealing mechanism portion for hermetically sealing the process chamber and the cover member, the hermetically sealing mechanism portion having: a gas passage defined between the process chamber and the cover member, an O-ring made of synthetic resin for sealing the gas passage, and an aluminum oxide layer formed at least in an area of the gas passage with which the O-ring is brought into contact.
 7. The pressure-reducible processing apparatus as recited in claim 6, wherein the aluminum oxide layer comprises an anodized film produced by anodizing a surface of the process chamber made of aluminum alloy with a nonaqueous solvent.
 8. The pressure-reducible processing apparatus as recited in claim 6, wherein the aluminum oxide layer comprises a protective film of aluminum oxide formed on a surface of stainless steel containing aluminum.
 9. The pressure-reducible processing apparatus as recited in claim 6, wherein the O-ring is made of synthetic resin of perfluoroelastomer.
 10. The pressure-reducible processing apparatus as recited in claim 6, wherein the hermetically sealing mechanism portion has a sealing cover provided between the O-ring and outside air.
 11. The pressure-reducible processing apparatus as recited in claim 6, wherein the O-ring is compressed at a compressibility of 10% to 30%. 